• Steven Rostedt's avatar
    tracing/fgraph: Add max_graph_depth to limit function_graph depth · 8741db53
    Steven Rostedt authored
    Add the file max_graph_depth to the debug tracing directory that lets
    the user define the depth of the function graph.
    
    A very useful operation is to set the depth to 1. Then it traces only
    the first function that is called when entering the kernel. This can
    be used to determine what system operations interrupt a process.
    
    For example, to work on NOHZ processes (single tasks running without
    a timer tick), if any interrupt goes off and preempts that task, this
    code will show it happening.
    
      # cd /sys/kernel/debug/tracing
      # echo 1 > max_graph_depth
      # echo function_graph > current_tracer
      # cat per_cpu/cpu/<cpu-of-process>/trace
    
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    8741db53
trace_functions_graph.c 36.1 KB